Plug valve

ABSTRACT

An eccentric plug valve and method for assembly wherein the valve utilizes a replaceable valve set which is placed against a gasket held in a groove about a rim of a valve opening within the valve body and the valve seat is held in position by means to fasten one side of the insert to the valve body and by a groove in the bottom of the valve cavity and a cam ledge on a valve cover which engage the bottom and top edges of the insert, respectively.

The present invention relates generally to valves and more particularlyto an improved rotary eccentric plug valve with a replaceable valve seatmounted to the valve body and a method of assembling the valve withreplaceable seat.

BACKGROUND OF THE INVENTION

Eccentric rotary plug valves are well known and represent a highlydeveloped area of technology. In such valves a plug or closure member ismounted for rotation in a generally cylindrical body with the axis ofplug rotation slightly offset from the axis of the valve body, or morespecifically, offset from the axis of that part of the body againstwhich the plug closes--hence the eccentric nature of the valve.

Plug valves have inlets and outlets which usually are aligned andtypically are sized to connect with pipes ranging from 3 to 48 inches indiameter. Normally the plug or closure member is rotated from an openposition, at one side of the cylindrical valve body, toward the interiorface of the valve inlet where it becomes seated to fully close thevalve. So as to minimize sliding contact of the respective plug andmating seat surface and provide seating adjustment, it has been known tomake that portion of the interior cylindrical surface surrounding thevalve inlet slightly eccentric to the valve body axis (such as bygenerating that portion of the interior surface from an axis offset fromthe axis of plug rotation), and to also make the correspondingcylindrical closure face of the plug slightly eccentric to the axis ofrotation which, in this construction may coincide with the valve bodyaxis. The seating end of the valve is hereinafter referred to as theinlet end; however, it may actually be at either the inlet or outlet enddepending on the orientation of the valve in the pipeline.

Most often either the plug or mating body seat surfaces have fused orwelded seats of relatively harder and resistant metal which are machinedin plate to a smooth finish. Such seats have several disadvantagesincluding high manufacturing cost, corrosion susceptibility anddifficulty, if not impossibility, to replace or renew upon excessivewear. Also when the valve seat is at the inlet end, hydraulic pressureagainst the plug of the closed valve tends to separate the plug from thebody seat and if any play develops in the plug, there will be leakagearound the seat. U.S. Pat. No. 2,574,428 appears to disclose areplaceable composite valve seat which positions a resilient ring forcontact by a cast plug closure which is not described in detail. U.S.Pat. No. 4,697,786 discloses a recent attempt to devise at least oneform of a replaceable plug valve seat. However, that form of valverequires a composite machined metal plug closure, and the replaceableseat in the valve body inlet is believed likely to be displaced by thepressure of liquid as the valve is partially opened.

SUMMARY OF THE INVENTION

Accordingly, it is a principle object of the present invention toprovide an improved valve and method of assembly wherein a valve seat inthe valve body adjacent the inlet is replaceable.

It is another object of the present invention to provide an improvedplug valve with a replaceable seat in the valve body and a resilientlycoated mono-metal plug closure to fit and seal against the replaceableseat.

It is a further object of the present invention to provide an improvedplug valve with a replaceable seat in the valve body which seat isarranged to utilize any displacement by hydraulic forces so as to selfseal against the plug closure member.

It is still another object of the present invention to provide animproved plug valve with a replaceable seat in the valve body whereinthe valve body and plug components each may be of cast single metal andnone of the closure cast surfaces need be machine finished.

Briefly stated the present invention is an assembled valve, particularlya plug valve, utilizing body, plug and cover parts which are each castof a single metal and (other than cover and connecting flanges),requiring a machine finish on a minimum of interior components such ason the plug shafts and mating body and cover trunnions, and wherein areplaceable, relatively flexible, seat is held against a resilientgasket laid in a groove cast in the valve body about the interior of thevalve inlet opening.

The upper and lower edges of the metal seat are held against the gasketby ledges in the valve body bottom and the valve cover; and preferablythe replaceable seat is secured to the valve body at a far side of theseat, in the direction of clossing movement of the plug closure member.

A preferred method to assemble the valve is to insert the replaceableseat against a ledge in the valve body bottom, also insert the plugclosure member into the valve body in an open position and piloting acover member on to the valve body with an internal ledge angularlyoffset from the bottom ledge, and then rotating the cover so as to alignthe ledges and press and secure the upper edge of the metal seat againstthe gasket.

BRIEF DESCRIPTION OF THE DRAWINGS

Further object and advantages of the present invention will becomeapparent from the following detailed description when read inconjunction with the drawings wherein:

FIG. 1 is a top plan view of an assembled preferred plug valveembodiment of the present invention;

FIG. 2 is a sectional elevation view of the valve taken at line 2--2 inFIG. 1;

FIG. 3 is a front elevation of a metal seat insert appearing partly insection in FIG. 2;

FIG. 4 is a sectional view of the metal seat insert taken at line 4--4in FIG. 3;

FIG. 5 is a plan view of a valve body according to the embodiment ofFIG. 1 with other parts removed;

FIG. 6 is a sectional elevation view of the valve body taken at line6--6 in FIG. 5;

FIG. 7 is a top plan view of a valve cover member removed from theembodiment of FIG. 1;

FIG. 8 is a bottom plan view of the valve cover member shown in FIG. 7;

FIG. 9 is a detailed side elevation view of a plug closure memberremoved from the embodiment of FIG. 1; and

FIG. 10 is a top plan detailed view of the plug closure member of FIG.9.

DETAILED DESCRIPTION OF THE INVENTION

Referring first to FIGS. 1 and 2 of the drawings it will be seen that apreferred embodiment of the present invention is a plug valve generally20 comprising a cast iron body 22, having aligned inlet and outletflanges 24, 26 at opposite ends, a cover 28 secured to an upper flange30 of the valve body 22 by a plurality of bolts 32 and a plug closuremember generally 40 positioned within the valve body 22 with a driveshaft 42 extending upwardly through a trunnion opening 46 in cover 28.

The plug closure member generally 40 is rotatable about a vertical axis(the axis of drive shaft 42) which, in this embodiment, also correspondsto an axis A--A of a substantially cylindrical cavity 50 within thevalve body 22 and the cover 28 and upper cover flange 30. A lower shaft54, extending beneath the plug closure member 40, is seated in a lowertrunnion 56 which is formed in the bottom wall 58 of valve body 22; andan offset crank arm 60 interconnects the drive shaft 42 and shaft 54.

As may be seen in FIG. 2 the cover trunnion 46 may be provided with asleeve bearing 66 and similarly a sleeve bearing 68 may be provided inlower trunnion 56 to reduce the force needed to move the plug closuremember 40. Additionally, a packing gland 70 is secured to the cover 28concentric to the drive shaft 42. Within the valve body 22 there areflared inlet and outlet passageways 74, 76 extending from the inletflange 24 and outlet flange 26, respectively, to the cavity 50. (Eachflange 24, 26 may contain bolt holes for connection to mating pipeflanges--not shown.) As seen in FIGS. 2 and 6 there is an interior inletrim 80 of the cavity 50, peripheral to the junction with inletpassageway 74, with a resilient gasket 82 seated in a groove 84 formedin the rim; and a relatively thin somewhat flexible and removable valveseat generally 90 overlaps the gasket 82. It is preferred that thegroove 84 be non-rectangular in cross section, that is the groove shouldadvantageously have a "V" or curved cross section, so as to enablecompression of the gasket to the point that the seal insert 90 willfully contact the inlet rim. This cross section also allows for castingdraft thereby eliminating additional core mold pieces.

It is understood that while a preferred embodiment of a valve isdescribed herein with reference to the valve seat being located at thevalve inlet, it is also possible to reverse the structure so as toorient the valve seat to the outlet end. Also it is to be understoodthat a preferred valve seat 90 is comprised of a metal such as stainlesssteel, however, it is within the scope of the invention to use othermaterials such as plated metal, coated metal and non-metalliccompositions.

As best shown in FIGS. 3 and 4 the removable valve seat insert generally90 is a rectangular web (part cylindrical in transverse direction so asto conform to the shape of the cavity 50) having a central opening 92,upper and lower edges 94, 96 and two sides 98, 100. The opening 92 isshaped to closely correspond to the juncture of cavity 50 and inletpassageway 74. Preferably one side 100 of the valve seat insert 90 isconfigured to accommodate means to fasten the insert to the interior ofthe valve body 22. In the illustrated preferred embodiment suchfastening means is in the form of a pair of threaded bolts or screws,not shown, and the valve seat insert is provided with a pair of boltholes 102, 104. As will become clear it is preferred that the valve seatinsert 90 have a degree of flexibility and the thickness of the insert90 is largely determined by that criterion. Furthermore, the valve seatinsert 90 is fabricated from a material, usually metal, that permitssuch flexibility and, more importantly, has characteristics appropriateto the fluid to flow through the valve. Thus the material may be chosento be non-reactive and/or corrosion resistant and the like. Stainlesssteel may readily be employed.

The interior of the valve body 22 is best seen in FIGS. 5 and 6. Groove84 (for gasket 82) and threaded holes 112 and 114 for valve insertfasteners are illustrated in FIG. 6. The cylindrical form of the valvebody cavity 50 generated from axis A--A is apparent in FIG. 5 althoughit will be noted that a portion of the cavity wall 118 surrounding theinlet passageway 74, and extending beyond the inlet rim 80 projectsinwardly. That portion 118 is also essentially cylindrical but isgenerated from an axis B slightly offset from axis A--A (points B and Ain FIG. 5). On the bottom wall 58 of the valve body 22 there is anarcuate foot ledge 122 that is concentric with cavity wall portion 118and slightly inward thereof so as to leave a small gap to receive thelower edge 96 of the valve seat insert 90.

Referring now to FIGS. 2, 7 and 8 for details of the valve covergenerally 28, it will be seen that a plurality of upwardly extendingdogs 130 may be provided for the purpose of interconnecting with a valveactuator which functions to mechanically move the plug closure member40. The inner face of the cover 28 includes an outer annular land 132and an inwardly extending shoulder 134 that holds a seal ring 136 insealing engagement with the valve body. Along one portion of the cover28 inner face that is intended to be positioned adjacent the valve inlet74 there is another arcuate ledge 142 having a cam face 144. The ledge142 will essentially correspond to ledge 122 on the bottom 58 of valvebody 22, when the cover 28 is secured in place, and thereby engage thecam face 144 with the upper edge 94 of the valve seat insert 90 to pressit against the gasket 82.

In FIGS. 9 and 10 details of the plug closure member generally 40 may beseen. The drive shaft 42 is provided with a keyway 150 so that it may beengaged by a valve actuator (not shown) or suitable wrench for turningthe shaft and plug closure member. As described hereinbefore the driveshaft 42 extends through the cover 28 and an aligned shaft 54 is seatedin trunnion 56 at the bottom wall 58 of the valve body 22. Theinterconnecting crank arm 60 functions to close and open the valve inletupon appropriate rotation of the drive shaft 42. To that purpose thecrank 60 includes a relatively broad and cylindrical outer face 154which is generated from an axis C (shown in FIG. 10) slightly offsetfrom the axis A of shafts 42 and 54 (which correspond to the main axisA--A of the valve cavity 50 when assembled) so that it will be congruentwith the cavity wall portion 118 when the valve parts are assembled andclosed.

Additionally the crank face 154 preferably has an embossment 156 whichis shaped to mate with the central opening 92 in the valve seat insert90. Further it is preferred that the entire crank face 154 andembossment 156, are covered with a layer 158 comprised of a resilientsubstance such as rubber or plastic so as to better fit and seal againstthe opening 92 in the valve seat insert 90 when closed thereon. It willbe understood that the plug closure member generally 40 is rotatedbetween a valve open position, where the crank 60 is to one side of theinlet opening (e.g. downwardly with respect to FIGS. 1 and 5), and avalve closed position, where the crank 60 is toward the inlet passageway74 with the face 154 aligned therewith (e.g. as shown in FIG. 2 and tothe left in FIGS. 1 and 5).

The aforedescribed valve may be assembled from the illustrated parts byan advantageous and novel method. Firstly the gasket 82, which isessentially in the form of a large O-ring, is laid in the groove 84 atthe inlet rim 80. Next the valve seat insert 90 is laid over the gasket82, convex surface toward the inlet with its lower edge 96 inserted inthe gap between bottom ledge 122 and the cavity wall portion 118. Then,if fastening means such as bolts or screws are to be employed, thefasteners are emplaced to secure the far side 100 (respecting plugclosure movement) of the insert 90 to the valve wall. The foregoingsteps may conveniently be undertaken with the valve axis A--A horizontaland the inlet flange 24 downward; and if so the valve body 22 may nextbe conveniently turned upright to place the axis A--A vertically.

The plug closure member generally 40 is then inserted into the valvecavity 50 with the crank face 154 turned to the open position and thestub shaft 54 inserted into the bearing 68 in trunnion 56. Then thecover 28 is fitted over the drive shaft 42 and, most importantly, thecover is oriented to generally register the arcuate ledge 142 with theoutlet passageway 76 of the valve body 22. While so oriented the cover28 is fully entered into the upper cover flange 30 of the valve body 22and only then is the cover rotated about axis A--A so as to align itsarcuate ledge 142 with inlet passageway 74 and the arcuate ledge 122 onthe bottom 58 of the valve body. The latter movement of the cover 28causes the cam face 144 of ledge 142 to engage and slide across theinner face of the upper edge 94 of valve seat insert 90. This results inthe upper part of the insert 90 being pressed forcefully against thegasket 82 and held in that position. The cover 28 is then secured, as bybolting, to flange 30.

Thereafter the plug closure member 40 may be operated and the assembledvalve may be installed with piping connected to the inlet and ouletflanges 24, 26. It is to be understood that when the plug closure member40 is moved to the closed position, sliding movement between crank face154 and the inner surface of valve seat insert 90 is minimal due to theeccentric construction heretofore described. The fastening meanssecuring side 100 of the seat insert 90, being on the far siderespecting movement of plug closure member 40, never contacts orinterferes with the crank face 154 or coating layer 158. Notably thehydraulic pressure in the pipe connected to valve inlet flange 24, whichis exerted against the crank face 154, will not cause separation of thatface 154 from the valve seat, but instead will tend to cause the valveseat to flex at the central opening 92 against the face 154 and theresilient coating layer 158 thereon. Such hydraulic pressure will alsoapply against the gasket 82 and thereby tend to force the gasket frombetween the groove 84 and valve seat insert 90 and into the valve cavity50 when the valve is rapidly opened. This tendency is particularlybothersome during the period that the valve is partially open andespecially as the opening movement of plug closure member 40 iscommenced. However, in the present valve structure the fastening meansprevents flexing of the mid portion of side 100 of insert 90 and theledges 142 and 122 and the crank face 154, itself, hold the top andbottom edges 94, 96 and other side 98 of the valve seat insert 90against flexure and thereby prevents loss of the gasket 82.

The foregoing preferred embodiment may be modified without departingfrom the spirit and scope of the invention which is defined in thefollowing claims.

What is claimed is:
 1. An improved valve wherein a valve closure memberis rotatable within a cavity of a valve body so as to move from one sideof said valve body to oppose one of an inlet and outlet rim in a wall ofsaid cavity, said improvement comprising:a peripheral groove formed inthe one rim; a resilient gasket laid in said groove; and a thinreplaceable seat insert placed over said gasket within said cavity so asto overlay said one rim, said groove and said gasket therein, whereby toboth receive said closure member when rotated to oppose said one rim andcompress said gasket to form a seal between said insert and said rim. 2.The valve of claim 1 wherein said seat insert has a central openingcorresponding to an opening in said valve body.
 3. The valve of claim 2wherein said seat insert is non-planar and shaped to generallycorrespond to the interior of said cavity adjacent said one rim.
 4. Thevalve of claim 1 wherein said peripheral groove is of non-rectangularcross section.
 5. The valve of claim 2 wherein said seat insert isrelatively flexible.
 6. The valve of claim 2 wherein said seat insert iscomprised of metal.
 7. The valve of claim 1 including a cover member forsaid valve body to enclose said cavity, said cover member having a camledge on the interior surface thereof, said cam ledge fitting withinsaid cavity and positionable to press an upper edge of said seat inserttoward said gasket and said one rim.
 8. The valve of claim 1 includingmeans to removably fasten said seat insert to the interior of saidcavity.
 9. The valve of claim 8 wherein the said means is located alongone side of said seat insert opposite to said one side of said valvebody.
 10. The valve of claim 9 wherein the said means consists of atleast one screw extending through a hole in said seat insert into saidvalve body.
 11. The valve of claim 1 including a resilient coating onsaid closure member so as to be compressible against said seat insert.12. The valve of claim 11 including a raised face on said closuremember, said raised face being of a shape and position on said closuremember so as to fit an opening in said seat insert.
 13. An improved plugtype valve wherein a valve closure member is rotatable within agenerally cylindrical cavity of a valve body about an axis offset froman axis of said cavity so as to move from one side of said valve body tooppose one of an inlet and outlet rim in a wall of said cavity, saidimprovement comprising:a peripheral groove formed in the one rim; aresilient gasket laid in said groove; a thin seat insert placed oversaid gasket within said cavity so as to overlay said one rim and saidgroove, said seat insert having an upper edge, a central openingcorresponding to an opening in said valve body, and having a curvedcross section so as to generally conform to said cavity wall and beingrelatively flexible, whereby to receive said closure member when rotatedto oppose said one rim and form a seal therebetween; and a cover memberfor said valve body to enclose said cavity, said cover member having acylindrical lip and interior surface fitting within said cavity and acam ledge on a peripheral portion of said interior surface engageablewith said upper edge of said thin seat insert to press said upper edgeagainst said gasket and said one rim.
 14. The plug valve of claim 13wherein said seat insert is metallic.
 15. An improved plug type valvewherein a valve closure member is rotatable within a generallycylindrical cavity of a valve body about an axis offset from an axis ofsaid cavity so as to move from one side of said valve body to oppose aninlet rim in a wall of said cavity, said improvement comprising:aperipheral groove of non-rectangular cross section formed in the inletrim; a resilient gasket laid in said groove; a thin metal seat insertplaced over said gasket within said cavity so as to overlay said inletrim and said groove, said seat insert having a central openingcorresponding to an inlet opening in said valve body, and having acurved cross section so as to generally conform to said cavity wall andbeing relatively flexible, whereby to receive said closure member whenrotated to oppose said inlet rim and form a seal therebetween; andfastening means to secure said metal seat insert to said cavity wall,said fastening means comprising at least one screw extending through ahole on a far side of said metal seat insert with respect to said oneside of said valve body; a raised face on said closure member, saidraised face being of a shape and positioned on said closure member so asto fit the central opening in said metal seat insert; and a resilientcoating on said closure member and about said raised face so as to becompressible against said metal seat insert.
 16. The plug valve of claim15 including an arcuate groove in a bottom of said valve cavity, saidgroove being adjacent said inlet rim and generally congruent therewithand receiving a lower edge of said thin metal seat insert.
 17. The plugvalve of claim 15 wherein said peripheral groove is of non-rectangularcross section.